Abstracts of Papers Published by SES (2008)

GMR of Stranded Multizone Conductors

Y. Yang, S. Fortin, J. Ma and F. P. Dawalibi

The 4th IASTED Asian Conference on Power and Energy Systems (AsiaPES), Langkawi, Malaysia, April 2 - 4, 2008.

Abstract: This paper presents a complete solution for the computation of the GMR of stranded conductors of circular cross-section, taking the frequency dependence (skin effect) into account. The stranded conductors can consist of several zones; the radius, resistivity and permeability of the strands can be different for each zone. Results for the GMR of various conductor configurations computed with this method are presented as a function of frequency. The computation results are in good agreement with published data. 

Grounding System Design for a Large Power Plant

J. Ma and F. P. Dawalibi

The 4th IASTED Asian Conference on Power and Energy Systems (AsiaPES), Langkawi, Malaysia, April 2 - 4, 2008.

Abstract: The grounding system design of a large power plant is described and discussed. Major procedures necessary for the design of an extensive grounding system are demonstrated. These procedures include constructing adequate soil structures based on short and long traverse soil resistivity measurements, conducting fault current distribution calculations, designing the grounding system, and performing the safety evaluations of the grounding system. The procedures presented in this paper can be used as a guide when designing extensive grounding systems in large power plants.

Parametric Analysis on Ground Level Safety Near Steel Poles Under Fault Conditions

Y. Li, J. Ma and F. P. Dawalibi

The 4th IASTED Asian Conference on Power and Energy Systems (AsiaPES), Langkawi, Malaysia, April 2 - 4, 2008.

Abstract: When a fault occurs on a distribution or transmission steel pole, the faulted pole or the adjacent poles can be subjected to very high ground potential rise. The earth surface voltage gradient near the tower is increased and could represent a hazard for a worker or a person who is touching the pole or just happens to be nearby. Appropriate pole grounding design may represent a relatively simple, durable, and economic solution. This paper carries out a detailed parametric analysis that shows how the grounding system can effectively reduce the touch and step voltages on the pole ground level. Generally speaking, installing a buried grounding loop around the pole decreases the touch voltages but increases the step voltages. Increasing the grounding system radius can improve the touch voltage tremendously without increasing significantly the step voltage. Significant variations in soil resistivity with depth have important impact on the performance of the grounding system. Burying the grounding system in a relative low soil resistivity layer can maximize the effectiveness of the grounding system for both touch and step voltages. Not surprisingly, the presence of bare metallic pipes in a residential or urban areas improves the touch and step voltages considerably.

Effects of Seasonal Variations on High Voltage Substation Grounding Grids Measured and Computed Results

S. Tee, F. P. Dawalibi and R. Yonza

The 4th IASTED Asian Conference on Power and Energy Systems (AsiaPES), Langkawi, Malaysia, April 2 - 4, 2008.

Abstract: The primary objective of this paper is to realistically assess the impact on the overall ground system performance and measurements of a transmission station due to a complex environment including; a very inhomogeneous soil structure, a microwave site, an auxiliary ground site, a nearby lake and slag pool, multiple transmission line equipped with skywires, a distribution line neutral, pole grounds and a neighboring town distribution network while accounting for significant seasonal resistivity variations of top soil layers as required by IEC Standard 61936-1. Since the present North American high voltage substation grounding standards (ANSI/ IEEE Standards 80 and 665, respectively) do not directly address this issue and very little information exists in other grounding literature, this study focuses on the behavior and safety of the grounding system in summer, winter and spring soil conditions.

Influence of Soil Characteristics on the Impedance of Aboveground and Buried Wires in Multilayer Horizontal Soil Model Environments

H. Zhao, S. Fortin and F. P. Dawalibi

The 4th IASTED Asian Conference on Power and Energy Systems (AsiaPES), Langkawi, Malaysia, April 2 - 4, 2008.

Abstract: The influence of soil parameters (resistivity, permittivity, permeability and thickness of the soil layers) on the longitudinal impedance of aboveground and buried wires is presented for the first time for arbitrary horizontal multilayer soil models based on a rigorous and general solution developed by the authors. Detailed computation results are presented for typical stratified earth with different layer parameters. The results show marked differences in the earth return impedances when compared to the case of homogeneous soils. The analysis shows the influence of each parameter and reveals that layer thickness, resistivity and permeability are significant factors to the longitudinal impedance, especially for buried wires.

Grounding Analysis of Large Hydroelectric Generating Complex Using Soil Structure Containing Heterogeneous Volumes

F. P. Dawalibi, N. Mitskevitch and G. Allard

The 17th Conference of the Electric Power Supply Industry (CEPSI), Macau, October 27 - 31, 2008. 

Abstract: This paper describes the evolution of Hydro-Quebec grounding analyses of the Eastmain hydroelectric complex (two power plants and two substations for a total of 1250 MW generating capacity) using a 7 km long wire electrode immersed in the upstream water reservoir. The analysis began in 2002 using a soil structure model that allow finite heterogeneous soil volumes and was analyzed again in 2005 using a new adaptive patch subdivision algorithm. The results are also compared to a preliminary study made in 1995 using a software package that supports a standard 2 layer soil model only. The paper describes and discusses the major differences between results computed using a classical grounding analysis package that assumes equipotential grounding electrode systems and a more accurate one that does not require this simplification. Furthermore, the paper demonstrates the effectiveness of heterogeneous soil volumes to analyse large hydroelectric power stations and confirm that the more accurate grounding package is best suited for this kind of analysis where large circulating currents can flow within the ground conductors.

Analysis and Validation of the Performance of Grounding Systems Buried in Soil Structures Containing Heterogeneous Volumes II

F. P. Dawalibi and N. Mitskevitch

The 17th Conference of the Electric Power Supply Industry (CEPSI), Macau, October 27 - 31, 2008. 

Abstract: This paper focuses on the performance of grounding systems in soil models containing heterogeneous finite soil volumes that have resistivity values different from that of the bulk volume of surrounding soil (native soil). This type of soil structure allows the study of a range of grounding problems that cannot be approximated by other known soil structures. This paper focuses on the class of problems that involve multiple soil volumes by describing and discussing the computed results and also by comparing them to some known limiting case solutions.

Application of Advanced Simulation Methods and Design Techniques to Interconnected Grounding Systems

J. Ma, J. Liu and F. P. Dawalibi

The 17th Conference of the Electric Power Supply Industry (CEPSI), Macau, October 27 - 31, 2008. 

Abstract: Advanced grounding simulation methods and design techniques, used to complete

a grounding system design for a gas insulated switching substation and an adjacent distribution substation in an urban area are presented in this paper. Soil resistivity test data interpretation and fault current distribution calculations were carried out. The grounding system and surrounding water pipe network were modeled first to compute conductor potentials, touch and step voltages. The GIS (Gas Insulated Substation) structure and GIS pipe enclosures were then modeled in detail to accurately compute GIS touch voltages. The method described here is an accurate and efficient approach to the analysis and design of interconnected grounding systems in urban areas involving gas insulated substations.

Effective Mitigation Designs for Pipelines and Railways Paralleling with the Power Lines

J. Liu, F. P. Dawalibi and J. Ma

The 17th Conference of the Electric Power Supply Industry (CEPSI), Macau, October 27 - 31, 2008. 

Abstract: Electromagnetic interference caused by electric transmission and distribution lines on neighboring utilities such as pipelines and railways is becoming a major concern due to the significant increase in power capacity and congestion of right of ways. This paper presents a typical study of electromagnetic interference on pipelines and railways caused by power lines under steady state and fault conditions with a particular emphasis on the mitigation design. An integrated software package that uses circuit based methods and 3D frequency domain grounding approach is used to accurately analyze complex electromagnetic interference issues and effectively reduce electromagnetic interference to acceptable levels, while yielding significant cost savings compared to alternative methods.

Automated Time-Domain Analysis of Transmission and Distribution Networks Using Circuit Models

Y. Li, F. P. Dawalibi, S. Fortin and J. Ma

The 17th Conference of the Electric Power Supply Industry (CEPSI), Macau, October 27 - 31, 2008. 

Abstract: A frequency domain analysis method for electric power line that yields an accurate time domain solution has been developed and is discussed in this paper. This method is applicable to large systems, and takes into account the frequency dependence of all circuit parameters and soil properties along the system as well as neighboring non electrified facilities that share the same right of way. The lightning strike current pulse is decomposed into its frequencies domain components using a forward Fourier transform. All relevant parameters used for modeling the right-of-way are taken into account in computing the line parameters, building the circuit model, and computing the induced voltages for each frequency. The time domain results are then obtained by taking an inverse Fourier transform. Two examples are presented: the first studies the propagation of a typical lightning pulse along the shield wire of a transmission line system and the second analyses the interference caused by this lightning pulse on a neighboring pipeline. The effectiveness of this method in providing an accurate time domain solution for systems involving complicated right-of-way is demonstrated.